Sodium bicarbonate has long been obtained from brine wells wherein hot water is pumped into subterranean mineral deposits, the sodium bicarbonate therein dissolves in the hot water and the resultant solution is pumped to the surface through a second well and, on cooling, the sodium bicarbonate precipitates and is isolated by filtration. In modern, commercial operations, the brine wells are operated at large volumes and the rate of filtration is critical to an economical process. Any modification that can accelerate the rate of slurry filtration is desirable. Furthermore, natural brines also contain sodium chloride as a contaminant which must be eliminated or at least reduced to a low level to produce an acceptable final product. Drying of the filter cake is also a costly operation and any procedure that will increase the drying rate increases the economic feasibility of the process.
Attempts to correct these three problems of slower than desirable filtration rates, sodium chloride contamination and excess filter cake moisture retention have comprised; 1) the use of additional filter equipment to handle the filtration volume but this results in longer slurry retention time in the filters; 2) the removal of salt by fresh water washes of the sodium bicarbonate brine cake but this results in a loss of sodium bicarbonate with the removal of sodium chloride and 3) the extension of the drying cycle but this results in longer drying times. All of these operations, moreover, have resulted in an added cost to the overall process.